With working dimensions of a silicon semiconductor, a magnetic device and the like reduced minutely and with high integration advanced, degradation in device characteristics and decrease in reliability have brought about more important problems than before. In recent years, in order to analyze defects of semiconductor device in a nanometer region and ascertain causes of defects thoroughly to solve them in the course of development of new processes and mass-production, spectral analysis and two-dimensional element distribution analysis using (scanning) transmission electron microscopy: (S) TEM) and electron energy loss spectroscopy: EELS) have become indispensable analysis means.
The electron energy loss spectrum can mainly be classified into a zero spectrum developing when passing through a sample do not loss energy, a plasmon spectrum obtained when electrons lose energy by exciting electrons in a valance electron band and an inner shell electron excitation loss spectrum obtained when electrons lose energy by exciting inner shell electrons. In the inner shell electron excitation loss (core loss) spectrum, a fine structure can be observed near an energy loss edge.
This structure is called an energy loss near-edge structure (ELNES) and has information reflecting the electron state and chemical bond state of a sample. The energy loss value (energy loss near-edge position) is inherent to an element and therefore, makes its qualitative analysis possible. Further, since information concerning coordination in the neighbor of a noticed element can be obtained from a shift of the energy loss near-edge position called a chemical shift, a simplified state analysis can be made.
Conventionally, when acquiring electron energy loss spectra at different locations on a sample, a scanning transmission electron microscope adapted to cause a finely focused electron beam to scan on the sample by means of a scanning coil and an electron spectrometer capable of performing spectroscopy by using an energy amount the electron beam has are used in combination in order that an electron beam having transmitted through the sample can undergo spectroscopy and electron energy loss spectra can be obtained in succession.
In the case of the above method, however, the aberration of electron energy loss spectrum and the origin position will change owing to a drift of accelerating voltage of the electron beam concomitant with a change in external disturbance in the neighbor of the apparatus and with changes in magnetic field and electric field, making it difficult to compare the shape of energy loss near-edge structure of electron energy loss spectrum and a slight chemical shift as well at a measurement location with those at another measurement location.
Then, Patent Literature 1, for example, describes a method according to which short-time measurements are conducted plural times by using a two-dimensional position detection device composed of a plurality of pixels and then, pixels at which the spectrum intensity of electron beam is maximized are detected in respect of detected values of the individual pixels in the individual measurements conducted plural times, the two-dimensional detection device is shifted so that pixel positions at which the spectrum intensity of electron beam is maximized in the individual measurements may coincide with each other, pixels whose positions are coincidental at that time are identified as pixels for the same energy value, and detection values in the individual measurements are integrated to make a long-time measurement possible.
For example, Patent Literatures 2 and 3 describe that a peak of spectrum is detected with an electron beam detector, a shift amount by which the peak position shifts from a reference location on the electron beam detector is detected, the shift amount is corrected by using an electron beam position control unit for controlling the electron beam position on the electron beam detector and besides, while controlling the correction of the peak position of spectrum for its shift amount and the spectrum measurement based on the electron beam detector, electron energy loss spectra are measured.
In the aforementioned technique, the energy shift (drift) concomitant to the change of apparatus external disturbance or the like during the measurement is corrected and then the electron energy loss spectra are measured but a spectrum used for detection of the shift amount and a spectrum associated with an analysis objective can not always be acquired at a time, making it difficult to correct the shift amount of peak position completely.
Further, electron energy loss spectra at a plurality of locations are not acquired at a time and so, when chemical shifts of electron energy loss spectra obtained at individual locations are compared with one another in detail, it is difficult as in the case of conventional techniques to decide whether the shift is due either to a chemical shift reflecting a difference in chemical bond state or to an external disturbance.
Then, Patent Literature 4, for example, describes that whilst a typical transmission electron microscope produces a transmission electron microscopic image for which focal positions in both the x and y axes are on the same plane, the aforementioned transmission electron microscope is provided with an electron spectrometer to make focal positions in x and y axes different from each other, thus ensuring that a two-dimensional image having a spectral plane at a focal position on x axis and an image plane at a focal position on y axis can be obtained with an image detector.
As a consequence, an electron energy loss spectrum in y direction of a sample can be separated and observed. In other words, the image obtained by means of the image detector can be observed as a spectral image showing an energy loss amount, that is, energy dispersion axis on x axis and showing position information of the sample on y axis as illustrated at (b) in FIG. 2. The spectral image is observed in a band form corresponding to individual laminated layer films of a transmission microscopic image as shown at (a) in FIG. 2. Then, when intensity profiles of the spectral image are extracted at individual locations corresponding to the respective laminated layer films shown at (a) in FIG. 2, electron energy loss spectra at different positions of the sample can be observed at a time as shown at (c) in FIG. 2, so that energy loss near-edge structures and slight chemical shifts of electron energy loss spectra at different positions can be compared with one another in detail.
The spectral image showing the energy loss amount on x axis and the position information of sample on y axis as described in Patent Literature 4 is a two-dimensional image obtained with the image detector by changing the lens function of the electron spectrometer or the like to make focal positions different in x and y axes, proving that electron energy loss spectra at plural different positions of the sample can be observed at a time. The conventional technique gives a disclosure of a technique aiming at the fact that spectral images, that is, electron energy loss spectra are captured from plural different points in a single sample to discus chemical shifts due to differences in chemical bond states but it fails to disclose that spectral images are obtained simultaneously from a plurality of samples to measure electron energy loss spectra and chemical shifts and hence, fails to obtain spectral images from the plural samples at a time.